This non-provisional application claims priority under 35 U.S.C. § 119(a) on Korean Patent Application No. 2003-83580 filed on Nov. 24, 2003, and Korean Patent Application No. 2004-95797 filed on Nov. 22, 2004 which are herein incorporated by reference.
1. Field of the Invention
The present invention relates to a method for forming an interlayer dielectric film for a semiconductor device by using a polyhedral molecular silsesquioxane. More specifically, the present invention relates to a method for forming a dielectric film by using a polyhedral molecular silsesquioxane as a monomer for a siloxane-based resin or as a pore-forming agent (hereinafter, referred to as a “porogen”) to prepare a composition for forming a dielectric film, and coating the composition on a substrate. Since the polyhedral molecular silsesquioxane used in the method contains a number of internal pores, a dielectric film formed by the method has a low dielectric constant. In addition, since a variety of reactive groups can be introduced into the polyhedral molecular silsesquioxane, the control over the reactive groups leads to a dielectric film having superior mechanical properties.
2. Description of the Related Art
With the increasing integration of semiconductor devices, the speed between wirings has a significant impact on the performance of the semiconductor devices. Accordingly, an interlayer dielectric film having a low storage capacity is required in order to lower the resistance and capacity between wirings. For this purpose, attempts have been made to use low dielectric constant materials for interlayer dielectric films. For instance, U.S. Pat. Nos. 3,615,272, 4,399,266, 4,756,977 and 4,999,397 disclose polysilsesquioxanes having a dielectric constant of about 2.5˜3.1 which can be applied by spin-on deposition (“SOD”), which can replace SiO2 having a dielectric constant of around 4.00 applied by a conventional chemical vapor deposition (CVD) technique. The compounds can be spin-coated due to their good planarizability.
On the other hand, hydrogen silsesquioxanes and a number of preparation processes thereof are well known in the art. For example, U.S. Pat. No. 3,615,272 teaches the production of a nearly fully condensed hydrogen resin by a process comprising hydrolyzing trichlorosilane in a benzenesulfonic acid hydrate hydrolysis medium and then washing the resultant resin with water or aqueous sulfuric acid. Further, U.S. Pat. No. 5,010,159 discloses a process for preparing a hydrogen silsesquioxane by hydrolyzing a hydridosilane in an arylsulfonic acid hydrate hydrolysis medium to form a resin, and contacting the resin with a neutralizing agent. Further, U.S. Pat. No. 6,232,424 suggests a highly soluble silicone resin composition having excellent solution stability which is prepared by hydrolyzing and condensing a tetraalkoxysilane, an organosilane and an organotrialkoxysilane in the presence of water and a catalyst. Further, U.S. Pat. No. 6,000,339 reports a process for preparing a silica-based compound which has improved oxygen plasma resistance and other physical properties, and enables thick-layer formation. According to this process, the silica-based compound is prepared by reacting a monomer selected from alkoxysilanes, fluorine-containing alkoxysilanes and alkylalkoxysilanes, with an alkoxide of titanium (Ti) or zirconium (Zr) in the presence of water and a catalyst. Further, U.S. Pat. No. 5,853,808 discloses siloxane and silsesquioxane polymers useful for preparing SiO2-rich thin films wherein the polymers are prepared from organosilanes having a β-substituted reactive group, and thin film compositions comprising the polymers. Further, EP 0 997 497 A1 describes a composition comprising an alkoxysilane compound selected from monoalkoxysilanes, dialkoxysilanes, trialkoxysilanes, tetraalkoxysilanes and trialkoxysilane dimmers, and an organic polymer. This patent further describes an insulating thin film formed by using the composition.
In an attempt to lower the dielectric constant of an interlayer dielectric film for a semiconductor device to 2.5 or lower, a porogen-template approach is suggested wherein the siloxane-based resin is formulated with a porogen and then the porogen is removed by thermal decomposition. However, problems encountered with this approach are that Si—OH bonds are formed on the pore surface, and the pore walls collapse and connect with one another during removal of the porogen, as depicted in FIG. 1. These problems degrade the process applicability of porous dielectric films to dielectric films for semiconductor devices.
For example, a great deal of research has been conducted on a cage-structured siloxane-based monomer having a diagonal length of about 5.3 Å, represented by the following Formula 1:
Formula 1

However, since a dielectric film formed using the siloxane-based monomer has a relatively high dielectric constant of 2.7˜3.0, the addition of a porogen is required in order to lower the dielectric constant. As a result, the above-mentioned problems inevitably occur.